Recent studies have revealed a relation between the given response and the response latency for personality questionnaire items in the form of an inverted-U effect, which has been interpreted in light of schema-driven behavior. In general, more probable responses are given faster. In the present study, the relationship between the probability of the given response and the response latency was investigated. First, a probabilistic model was introduced describing the relationship between response latencies and a latent trait. Second, the model was applied in an empirical study: Employing items from a personality questionnaire and using data from 170 men, the probability of responses were estimated based on the Rasch model. Assuming log-normally distributed response latencies, a linear regression model was fit to the logarithmized response latencies, including the response probability as a predictor. Findings suggested that the quantities are negatively related. This relation can be used to incorporate the response latency into the estimation of trait levels. For the scales used in the study, the results showed that test information could be increased by 13% to 17% when considering response latencies. (Contains 2 tables and 2 figures.)